This invention relates generally to improvements in so-called hydraulic cutting assemblies wherein a vegetable product such as a potato is propelled by a fluid such as water into cutting engagement with knife elements positioned along a fluid flow path to cut the product into elongated strips. More particularly, this invention relates to an improved hydraulic cutting system equipped with a deceleration conduit at a downstream side of the knife elements for controllably decelerating the cut product strips in a manner which substantially reduces or eliminates undesired strip breakage.
Hydraulic cutting systems in general are well known in the art, and typically comprise a so-called water knife fixture having one or more knife elements mounted along the length of an elongated tubular conduit. A pumping device is provided to entrain a vegetable product such as a potato within a propelling stream of water or the like for cutting engagement with the knife elements. In production systems, the product is pumped one at a time in relatively rapid single file succession into and through the conduit with a velocity and kinetic energy sufficient to carry the product past the knife elements so that the product is severed into a plurality of smaller elongated strips at a relatively high production rate. The particular size and shape of the cut product strips is dictated by the geometry of the knife elements, and these cut strips are carried further by the flow stream through a discharge conduit which guides the strips to subsequent processing equipment for size grading, cooking, freezing, packaging, and the like. Such hydraulic cutting systems are commonly used for cutting raw potatoes into elongated French fry strips. Examples of hydraulic cutting assemblies and related water knife constructions are found in U.S. Pat. Nos. 3,109,468; 3,116,772; 3,208,625; 4,082,024; 4,135,002; 4,372,184; and 4,423,652.
In such hydraulic cutting systems, the individual products such as potatoes propelled along the flow conduit are subjected to substantial hydraulic pressure forces as the potatoes travel from the pumping device to and through cutting engagement with the knife elements of the water knife fixture. For example, in a typical French fry processing line, the individual potatoes are entrained within the propelling water stream at a pressure of about 15-20 psi, and are rapidly propelled by the water stream into cutting engagement with the knife elements at a velocity of about 40-60 feet per second. However, as the cut potato strips exit the water knife fixture, the cross sectional size and shape of the flow path has typically expanded, to create a significant fluid pressure drop and related turbulent fluid flow in combination with a rapid velocity decrease at that location. As a result, the cut strips tend to tumble within the flow passage as the fluid pressure is released and as the strip velocity is reduced for delivery of the strips to subsequent processing equipment. Unfortunately, the combined effects of the fluid pressure drop and turbulent fluid flow at the downstream side of the water knife fixture contributes to an undesirably high incidence of strip breakage, which can be on the order of about 25% for smaller strip cut sizes. Such strip breakage creates an abundance of undesirably small cut pieces which negatively impacts the overall commercial quality and utility of the cut strips. Indeed, in many production systems, the cut product strips must be size-graded to remove small broken pieces from the production flow.
There exists, therefore, a need for improvements in and to hydraulic cutting systems for cutting products such as potatoes into elongated strips, particularly with respect to reducing and substantially eliminating strip breakage as the cut strips travel from a water knife fixture to subsequent processing equipment. The present invention fulfills this need and provides further related advantages.
In accordance with the invention, an improved hydraulic cutting system is provided for cutting a succession of vegetable products or the like particularly such as potatoes into elongated strips, wherein the cutting system includes a deceleration conduit designed for decelerating cut product strips substantially without rapid pressure drop or flow stream turbulence to reduce or eliminate strip breakage.
The cutting system utilizes a propelling hydraulic flow stream to propel the products with substantial velocity into and through cutting engagement with knife blade elements of a so-called water knife fixture mounted along the length of a fluid flow passage. The cutting system includes a pump for entraining the products one at a time within a fluid flow stream of water or the like for product flow at a substantial velocity along a delivery conduit to the water knife fixture mounted at a downstream end of the delivery conduit. In a preferred form, the delivery conduit and the water knife fixture define a flow passage of substantially constant cross section, so that the product is subjected to a substantially constant and uninterrupted fluid pressure. A centering or alignment fixture may be incorporated along the delivery conduit at an upstream side of the water knife fixture for substantially aligning each product with a centerline of the flow passage, immediately prior to product engagement with knife elements of the knife fixture for cutting each product into elongated strips.
The deceleration conduit defines a continuation of the fluid flow passage at a downstream side of the water knife fixture. This deceleration conduit is designed to reduce the velocity of the cut strips substantially to a relatively slow velocity compatible with strip conveyance to subsequent processing equipment, such as blanching and/or frying steps in the case of French fried potatoes, substantially without exposing the cut strips to a rapid pressure drop or turbulent water flow conditions which could otherwise cause strip breakage. The deceleration conduit has an elongated tapered shape which expands gradually in cross section relative to a conduit centerline at an angle not exceeding 9xc2x0 and preferably on the order of about 2xc2x0 to about 3xc2x0. In a preferred configuration, this tapered deceleration conduit is mounted in-line with and at a downstream end of a substantially nontapered or constant cross section transition conduit coupled in turn to the downstream side of the water knife fixture. The transition conduit has a length which is several times, preferably about 8 times, the diameter of the flow passage exiting the water knife fixture, and functions to maintain the fluid pressure applied to the cut strips for a sufficient time to enable the propelling fluid flow to re-stabilize at the downstream side of the knife fixture. Thereafter, the expanding tapered geometry of the deceleration conduit gradually reduces the flow velocity of the cut strips, and the fluid pressure applied thereto, substantially without strip turbulence or tumbling within the flow stream.
Other features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.